The Note A

A is the universal tuning reference. The A above middle C vibrates at 440 Hz — the standard concert pitch used worldwide to tune orchestras, pianos, and fretted instruments. A major sounds bright and assertive on guitar, with the root and fifth ringing on open strings; A minor, with no sharps or flats, is the gentlest of the minor keys — reflective rather than dark. Its reference octave pitch is 440 Hz (MIDI note 69). The major triad on A is A Major (A – C# – E), and the minor triad is A Minor (A – C – E).